package com.imddysc.springbootbatch001.utils;

import java.io.ByteArrayOutputStream;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;
import java.security.interfaces.DSAPrivateKey;
import java.security.interfaces.DSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

public class DSAUtils {

	public static final String KEY_ALGORITHM = "DSA";
	//public static final String SIGNATURE_ALGORITHM = "DSA";
	public static final String SIGNATURE_ALGORITHM = "SHA1withDSA";
	//private static final String DEFAULT_SEED = "0f22507a10bbddd07d8a3082122966e3";
	private static final int KEY_SIZE = 1024;
	private static final String PUBLIC_KEY = "DSAPublicKey";
	private static final String PRIVATE_KEY = "DSAPrivateKey";
	/**
	 * RSA最大加密明文大小
	 */
	private static final int MAX_ENCRYPT_BLOCK = 117;

	/**
	 * RSA最大解密密文大小
	 */
	private static final int MAX_DECRYPT_BLOCK = 128;

	public static String getPublicKey(Map<String, Object> keyMap) throws Exception {
		Key key = (Key) keyMap.get(PUBLIC_KEY);
		// byte[] publicKey = key.getEncoded();
		return Base64.getEncoder().encodeToString(key.getEncoded());
	}

	public static String getPrivateKey(Map<String, Object> keyMap) throws Exception {
		Key key = (Key) keyMap.get(PRIVATE_KEY);
		// byte[] privateKey = key.getEncoded();
		return Base64.getEncoder().encodeToString(key.getEncoded());
	}

	public static byte[] decryptBASE64(String key) throws Exception {
		// return (new BASE64Decoder()).decodeBuffer(key);
		return Base64.getDecoder().decode(key);
	}

	public static String encryptBASE64(byte[] key) throws Exception {
		// return (new BASE64Encoder()).encodeBuffer(key);
		return Base64.getEncoder().encodeToString(key);
	}

	public static Map<String, Object> initKey() throws Exception {
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
		keyPairGen.initialize(1024);
		KeyPair keyPair = keyPairGen.generateKeyPair();
		DSAPublicKey publicKey = (DSAPublicKey) keyPair.getPublic();
		DSAPrivateKey privateKey = (DSAPrivateKey) keyPair.getPrivate();
		Map<String, Object> keyMap = new HashMap<String, Object>(2);
		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);
		return keyMap;
	}
	
	public static Map<String, Object> initKey(String seed) throws Exception {
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
		SecureRandom secureRandom = new SecureRandom();
		secureRandom.setSeed(seed.getBytes());
		keyPairGen.initialize(KEY_SIZE, secureRandom);
		KeyPair keyPair = keyPairGen.generateKeyPair();
		DSAPublicKey publicKey = (DSAPublicKey) keyPair.getPublic();
		DSAPrivateKey privateKey = (DSAPrivateKey) keyPair.getPrivate();
		Map<String, Object> keyMap = new HashMap<String, Object>(2);
		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);
		return keyMap;
	}
	
	

	/**
	 * 用私钥对信息生成数字签名
	 * 
	 * @param data       已加密数据
	 * @param privateKey 私钥(BASE64编码)
	 * @return 返回签名字后Base64后的签名字符串
	 * @throws Exception
	 */
	public static String sign(byte[] data, String privateKey) throws Exception {
		// byte[] keyBytes = (new BASE64Decoder()).decodeBuffer(privateKey);
		byte[] keyBytes = Base64.getDecoder().decode(privateKey);
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
		Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
		signature.initSign(privateK);
		signature.update(data);
		// return (new BASE64Encoder()).encode(signature.sign());
		return Base64.getEncoder().encodeToString(signature.sign());
	}

	/**
	 * 校验数字签名
	 * 
	 * @param data      已加密数据
	 * @param publicKey 公钥(BASE64编码)
	 * @param sign      数字签名
	 * @return 校验签名
	 * @throws Exception
	 */
	public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {
		// byte[] keyBytes = (new BASE64Decoder()).decodeBuffer(publicKey);
		byte[] keyBytes = Base64.getDecoder().decode(publicKey);
		X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		PublicKey publicK = keyFactory.generatePublic(keySpec);
		Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
		signature.initVerify(publicK);
		signature.update(data);
		// return signature.verify((new BASE64Decoder()).decodeBuffer(sign));
		return signature.verify(Base64.getDecoder().decode(sign));
	}

	/**
	 * 私钥解密
	 * 
	 * @param encryptedData 已加密数据
	 * @param privateKey    私钥(BASE64编码)
	 * @return 返回解密后的字节
	 * @throws Exception
	 */
	public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey) throws Exception {
		// byte[] keyBytes = (new BASE64Decoder()).decodeBuffer(privateKey);
		byte[] keyBytes = Base64.getDecoder().decode(privateKey);
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.DECRYPT_MODE, privateK);
		int inputLen = encryptedData.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 对数据分段解密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
				cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_DECRYPT_BLOCK;
		}
		byte[] decryptedData = out.toByteArray();
		out.close();
		return decryptedData;
	}

	/**
	 * 公钥解密
	 * 
	 * @param encryptedData 已加密数据
	 * @param publicKey     公钥(BASE64编码)
	 * @return 返回解密后的字节
	 * @throws Exception
	 */
	public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey) throws Exception {
		// byte[] keyBytes = (new BASE64Decoder()).decodeBuffer(publicKey);
		byte[] keyBytes = Base64.getDecoder().decode(publicKey);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key publicK = keyFactory.generatePublic(x509KeySpec);
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.DECRYPT_MODE, publicK);
		int inputLen = encryptedData.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 对数据分段解密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
				cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_DECRYPT_BLOCK;
		}
		byte[] decryptedData = out.toByteArray();
		out.close();
		return decryptedData;
	}

	/**
	 * 公钥加密
	 * 
	 * @param data      源数据
	 * @param publicKey 公钥(BASE64编码)
	 * @return 返回加密后的字节
	 * @throws Exception
	 */
	public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {
		// byte[] keyBytes = (new BASE64Decoder()).decodeBuffer(publicKey);
		byte[] keyBytes = Base64.getDecoder().decode(publicKey);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key publicK = keyFactory.generatePublic(x509KeySpec);
		// 对数据加密
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.ENCRYPT_MODE, publicK);
		int inputLen = data.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 对数据分段加密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
				cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(data, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_ENCRYPT_BLOCK;
		}
		byte[] encryptedData = out.toByteArray();
		out.close();
		return encryptedData;
	}

	/**
	 * 私钥加密
	 * 
	 * @param data       源数据
	 * @param privateKey 私钥(BASE64编码)
	 * @return 返回加密后的字节
	 * @throws Exception
	 */
	public static byte[] encryptByPrivateKey(byte[] data, String privateKey) throws Exception {
		// byte[] keyBytes = (new BASE64Decoder()).decodeBuffer(privateKey);
		byte[] keyBytes = Base64.getDecoder().decode(privateKey);
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.ENCRYPT_MODE, privateK);
		int inputLen = data.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 对数据分段加密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
				cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(data, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_ENCRYPT_BLOCK;
		}
		byte[] encryptedData = out.toByteArray();
		out.close();
		return encryptedData;
	}

	public static void main(String[] args) {
		
		System.out.println("这里这个DSA 只有验签哦，加解密没有");
		
		Map<String, Object> keyMap;
		try {
			keyMap = initKey();
			String publicKey = getPublicKey(keyMap);
			System.out.println("publicKey: ");
			System.out.println(publicKey);
			String privateKey = getPrivateKey(keyMap);
			System.out.println("privateKey: ");
			System.out.println(privateKey);
		} catch (Exception e) {
			e.printStackTrace();
		}

		System.out.println("-----------------------------------------");
		Map<String, Object> keyMapA;
		Map<String, Object> keyMapB;
		try {
			keyMapA = initKey();
			keyMapB = initKey();
			System.out.println(keyMapA.equals(keyMapB));

			String ApublicKey = getPublicKey(keyMapA);
			String BpublicKey = getPublicKey(keyMapB);
			String AprivateKey = getPrivateKey(keyMapA);
			String BprivateKey = getPrivateKey(keyMapB);
			System.out.println("-------------");
			System.out.println("ApublicKey:" + ApublicKey);
			System.out.println("AprivateKey:" + AprivateKey);
			System.out.println("-------------");
			System.out.println("BpublicKey:" + BpublicKey);
			System.out.println("BprivateKey:" + BprivateKey);
			System.out.println("----------------------------------------");

			
			String source1 = "这个表要要加密的内容，我们现在开始处理，用B的私钥进行加密，然后得取字符串，发给A，A收到加密字符串后，利用B的公钥进行解密。";
			System.out.println("原文字：\n" + source1);
			byte[] data1 = source1.getBytes();
			
			System.out.println("私钥签名——公钥验证签名");
			String sign1 = sign(data1, BprivateKey);
			System.out.println("签名: \n" + sign1);
			boolean status2 = verify(data1, BpublicKey, sign1);
			System.out.println("验证结果: \n" + status2);

		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}
